The present invention relates to a high voltage transformer, and more particularly, to a high voltage transformer for use in a microwave oven.
A microwave oven cooks foods by dielectrically heating the foods by microwaves emitted from a magnetron thereof.
As shown in FIG. 1, a microwave oven generally includes a body frame 1 having a cooking room 5 and a component room 6, an external case 2 for surrounding the body frame 1, a door 3 for closing/opening the cooking room 5 and a control panel 4 for a user operation. Installed in the component room 6 are, a magnetron 7 for emitting a microwaves, a high voltage transformer 8 for generating a necessary voltage between positive and negative electrodes of the magnetron 7, a high voltage capacitor 9 for charging and discharging a high-voltage output of a secondary side of the high voltage transformer 8 to supply the high-voltage output to the positive electrode of the magnetron 7, and a cooling fan 10 for preventing the magnetron 7 from overheating Here, since the high voltage transformer 8 generates the necessary voltage to the positive and negative electrodes of the magnetron 7 from a commercial power source (AC 110/220 V), and especially generates the high voltage to the positive electrode of the magnetron 7 at the secondary side thereof, a superior insulation for the high voltage is required for the high voltage transformer 8 and it is necessary to handle the transformer carefully.
As shown in FIG. 5, a conventional high voltage transformer for a microwave oven includes a shell type core having an I-type core member 34a and an E-type core member 34b, primary and secondary coils 31 and 32 which are inserted into the core, and a heater coil 33 installed between the primary and secondary coils 31 and 32. Pass cores 42 and 42' are installed between the primary coil 31 and the heater coil 33 to fill up a space inside the core. For insulation with respect to the inner walls of the core, the primary and secondary coils 31 and 32 and the heater coil 33 are wrapped up in insulators 38 and 38', 39 and 39', 40 and 40', and 41 and 41', respectively. The pass cores 42 and 42' are insulated by mica sheets 43 and 43'.
Terminal boards 36 and 37 each having terminals 36a and 36a' and 37a and 37a' are attached to the primary and secondary coils 31 and 32 by an insulating tape (not shown), respectively. Lead wires 31a and 31a' and 32a and 32a' for the respective coils 31 and 32 are soldered to the terminals 36a and 36a' and 37a and 37a', respectively. The terminals 36a and 36a' of the primary terminal board 36 are connected to the external commercial power source and the terminals 37a and 37a' of the secondary terminal board 37 are connected to the high voltage capacitor.
In the above-described high voltage transformer, since the terminals, especially the secondary terminals at which the high voltage is induced are exposed to the outside, there is a probability of an electric shock, for example, in the state that the external case 2 is disassembled from the microwave oven for repair, as shown in FIG. 1.
Furthermore, for the installation of the terminal boards during assembling the high voltage transformer, the steps of soldering the lead wires of the coils to the terminals of the terminal boards, primarily attaching the insulating tape to the portions of the coils to which the terminal boards are attached and then fixing the terminal boards to the coils using the insulating tape are required. However, the taping processes are boresome and time-consuming.